Display device and electronic device
Summary by NHIP
Multi-line display device
The display device includes three or more data lines that partially overlap and intersect to connect closest to corresponding selection transistors. Each data line maintains substantially the same wiring resistance, and intersections contain a conductive layer matching the scan line material.
Claim Score by NHIP
Abstract
An object is to provide a display device in which a difference in load capacitance between wirings is reduced in the case where different signals are supplied to plural pixels at the same timing with use of plural wirings; thus, deviation in the grayscale and/or signal delay can be reduced. The display device includes first to N-th (N is a natural number of 3 or larger) data lines for supplying different video signals; and a pixel including a selection transistor connected to one of the first to N-th data lines. The first to N-th data lines intersect with each other so that one of the first to N-th data lines is provided closest to one terminal of the selection transistor and connected to the one terminal of the selection transistor.

Term
5.1 yearsleft in the term
Expires 1 November 2031, including 158 days of term adjustment.
- Priority
- Filed
- Granted
- Today
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12 claims: 2 independent, 10 dependent
- 1Broadest claimClaim Score 73, broad(NHIP)A display device comprising:first to N-th data lines, wherein N is a natural number of 3 or larger;and first to N-th selection transistors, wherein the first to N-th data lines partially overlap and intersect with each other so that each one of the first to N-th data lines is provided closest to a corresponding one of the first to N-th selection transistors and electrically connected to one of a source and a drain of the corresponding one of the first to N-th selection transistors.
- 8A display device comprising:first to N-th scan lines, wherein N is a natural number of 3 or larger;and first to N-th selection transistors, wherein the first to N-th scan lines partially overlap and intersect with each other so that each one of the first to N-th scan lines is provided closest to a corresponding one of the first to N-th selection transistors and electrically connected to a gate of the corresponding one of the first to N-th selection transistors.
Independent claims2
158 paragraphs in 5 sections, as filed
BACKGROUND OF THE INVENTION
00011. Field of the Invention
0002The present invention relates to a display device, a method for driving the display device, or an electronic device provided with the display device.
00032. Description of the Related Art
0004Display devices typified by liquid crystal display devices including liquid crystal elements, ranging from large display devices such as television receivers to small display devices such as cellular phones, have been spreading. From now on, products with higher added values will be needed and are being developed.
0005In order to add higher values, the number of wirings such as scan lines or data lines which supply signals to each pixel of a display device may be increased so that driving of a pixel is sophisticated. For example, Patent Document 1 discloses a display device provided with a plurality of data lines. In Patent Document 1, the connection between a transistor of a pixel and one of the plurality of data lines is disclosed.
REFERENCE
Patent Document 1
0000<ul id="ul0001" list-style="none"><li id="ul0001-0001" num="0006">Japanese Published Patent Application No. 2003-186451</li></ul>
SUMMARY OF THE INVENTION
0007As in Patent Document 1, in the case of increasing the number of wirings such as scan lines or data lines which supply signals to each pixel of a display device, a wiring is extended from a transistor of a pixel to connect with the wiring such as the scan line or the data line which supplies a signal to the pixel. With such a structure, there is a problem in that load capacitance differs between the wirings and thus malfunction in display might occur. The case where load capacitance differs between the wirings will be described below with reference to drawings.
0008<figref idref="DRAWINGS">FIG. 15A</figref> illustrates a circuit configuration of a pixel included in a display device. <figref idref="DRAWINGS">FIG. 15A</figref> illustrates a circuit configuration in the case where, specifically, three data lines as N (N is a natural number of 3 or larger) data lines (also referred to as signal lines) supply different video signals to three different pixels. A pixel <b>1501</b>A includes a transistor (also referred to as a selection transistor) <b>1504</b>A and a display element portion <b>1505</b>A. In the transistor <b>1504</b>A of the pixel <b>1501</b>A, a gate terminal is connected to a scan line <b>1503</b>A, one terminal (also referred to as a first terminal) to be a source terminal or a drain terminal is connected to a first data line <b>1502</b>A, and the other terminal is connected to the display element portion <b>1505</b>A. A pixel <b>1501</b>B includes a transistor (also referred to as a selection transistor) <b>1504</b>B and a display element portion <b>1505</b>B. In the transistor <b>1504</b>B of the pixel <b>1501</b>B, a gate terminal is connected to a scan line <b>1503</b>B, one terminal (also referred to as a first terminal) to be a source terminal or a drain terminal is connected to a second data line <b>1502</b>B, and the other terminal is connected to the display element portion <b>1505</b>B. A pixel <b>1501</b>C includes a transistor (also referred to as a selection transistor) <b>1504</b>C and a display element portion <b>1505</b>C. In the transistor <b>1504</b>C of the pixel <b>1501</b>C, a gate terminal is connected to a scan line <b>1503</b>C, one terminal (also referred to as a first terminal) to be a source terminal or a drain terminal is connected to a third data line <b>1502</b>C, and the other terminal is connected to the display element portion <b>1505</b>C. The above-described circuit configuration of <figref idref="DRAWINGS">FIG. 15A</figref> is effective in the case where, for example, the transistors <b>1504</b>A to <b>1504</b>C are brought into conduction (i.e., the transistors <b>1504</b>A to <b>1504</b>C are turned on) by scan signals through the scan lines <b>1503</b>A to <b>1503</b>C so that different video signals are supplied to the display element portions <b>1505</b>A to <b>1505</b>C through the first to third data lines <b>1502</b>A to <b>1502</b>C.
0009Specific description of display elements in the display element portions <b>1505</b>A to <b>1505</b>C is omitted. In the case of a liquid crystal display device, a liquid crystal element and a capacitor may be provided, and in the case of an EL element, a light-emitting element and a transistor for driving the light-emitting element may be provided.
0010When pixels are arranged in matrix, the first to third data lines <b>1502</b>A to <b>1502</b>C are provided in the direction substantially orthogonal to the scan lines <b>1503</b>A to <b>1503</b>C, and the pixel <b>1501</b>A including the transistor <b>1504</b>A, the pixel <b>1501</b>B including the transistor <b>1504</b>B, and the pixel <b>1501</b>C including the transistor <b>1504</b>C are provided along the first data line <b>1502</b>A, the second data line <b>1502</b>B, and the third data line <b>1502</b>C, respectively. Thus, in the case where the first to third data lines <b>1502</b>A to <b>1502</b>C are provided in parallel to each other, when one terminal of the transistor <b>1504</b>B is connected to the second data line <b>1502</b>B, an intersection portion <b>1506</b> illustrated in <figref idref="DRAWINGS">FIG. 15A</figref> is formed. Similarly, when one terminal of the transistor <b>1504</b>C is connected to the third data line <b>1502</b>C, an intersection portion <b>1507</b> illustrated in <figref idref="DRAWINGS">FIG. 15A</figref> is formed. In the intersection portion <b>1506</b> and the intersection portion <b>1507</b>, in order to avoid short-circuit between the first to third data lines <b>1502</b>A to <b>1502</b>C, a conductive layer is formed in another layer, whereby, through the conductive layer, the one terminal of the transistor <b>1504</b>B is connected to the second data line <b>1502</b>B, and the one terminal of the transistor <b>1504</b>C is connected to the third data line <b>1502</b>C.
0011However, when connection between one terminal of the transistor <b>1504</b>B and the second data line <b>1502</b>B and connection between one terminal of the transistor <b>1504</b>C and the third data line <b>1502</b>C are formed through the conductive layer, load capacitance <b>1516</b> due to the intersection portion <b>1506</b> and load capacitance <b>1517</b>A and <b>1517</b>B due to the intersection portion <b>1507</b> are formed as in <figref idref="DRAWINGS">FIG. 15B</figref>. Specifically, the load capacitance <b>1516</b>, the load capacitance <b>1517</b>A, and the load capacitance <b>1517</b>B differ from each other depending on the area of the intersection portion where the conductive layer intersects with the first to third data lines <b>1502</b>A to <b>1502</b>C. Thus, a difference in load capacitance is made between the first data line <b>1502</b>A and the second data line <b>1502</b>B, and it is difficult to supply a signal with a desired potential to each pixel. Such a problem causes deviation in the grayscale and/or signal delay.
0012In view of the above, an object of one embodiment of the present invention is to provide a display device in which a difference in load capacitance between wirings is reduced in the case where different signals are supplied to plural pixels at the same timing with use of plural wirings; thus, deviation in the grayscale and/or signal delay can be reduced.
0013One embodiment of the present invention is a display device including first to N-th (N is a natural number of 3 or larger) data lines for supplying different video signals; and a pixel including a selection transistor connected to one of the first to N-th data lines, in which the first to N-th data lines intersect with each other so that one of the first to N-th data lines is provided closest to one terminal of the selection transistor and connected to the one terminal of the selection transistor.
0014In the display device according to one embodiment of the present invention, a display element including a liquid crystal element may be connected to the other terminal of the selection transistor.
0015In the display device according to one embodiment of the present invention, a display element, including a light-emitting element and a driving transistor for driving the light-emitting element, may be connected to the other terminal of the selection transistor.
0016The display device according to one embodiment of the present invention may further include a scan line, in which an intersection portion between the first to N-th data lines may be a conductive layer that is the same as the scan line.
0017In the display device according to one embodiment of the present invention, the first to N-th data lines may have a uniform resistance caused by the conductive layer in the intersection portion.
0018One embodiment of the present invention is a display device including first to N-th (N is a natural number of 3 or larger) scan lines for supplying different scan signals; and a pixel including a selection transistor connected to one of the first to N-th scan lines, in which the first to N-th scan lines intersect with each other so that the one of the first to N-th scan lines is provided closest to a gate terminal of the selection transistor and connected to the gate terminal of the selection transistor.
0019In the display device according to one embodiment of the present invention, the one of the first to N-th data lines may be connected to one terminal of the selection transistor, and a display element including a liquid crystal element may be connected to the other terminal of the selection transistor.
0020In the display device according to one embodiment of the present invention, the one of the first to N-th data lines may be connected to one terminal of the selection transistor, and a display element, including a light-emitting element and a driving transistor for driving the light-emitting element, may be connected to the other terminal of the selection transistor.
0021According to one embodiment of the present invention, a difference in load capacitance between wirings is reduced; thus, deviation in the grayscale and/or signal delay can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
0022In the accompanying drawings:
0023<figref idref="DRAWINGS">FIGS. 1A and 1B</figref> are circuit diagrams according to one embodiment of the present invention;
0024<figref idref="DRAWINGS">FIGS. 2A and 2B</figref> are circuit diagrams according to one embodiment of the present invention;
0025<figref idref="DRAWINGS">FIG. 3</figref> is a top view according to one embodiment of the present invention;
0026<figref idref="DRAWINGS">FIGS. 4A and 4B</figref> are each a circuit diagram according to one embodiment of the present invention;
0027<figref idref="DRAWINGS">FIG. 5</figref> is a circuit diagram according to one embodiment of the present invention;
0028<figref idref="DRAWINGS">FIGS. 6A and 6B</figref> are circuit diagrams according to one embodiment of the present invention;
0029<figref idref="DRAWINGS">FIGS. 7A and 7B</figref> are each a circuit diagram according to one embodiment of the present invention;
0030<figref idref="DRAWINGS">FIGS. 8A to 8D</figref> are circuit diagrams according to one embodiment of the present invention;
0031<figref idref="DRAWINGS">FIGS. 9A and 9B</figref> are a circuit diagram and a timing chart, respectively, according to one embodiment of the present invention;
0032<figref idref="DRAWINGS">FIGS. 10A and 10B</figref> are a circuit diagram and a block diagram, respectively, according to one embodiment of the present invention;
0033<figref idref="DRAWINGS">FIG. 11</figref> is a timing chart showing one embodiment of the present invention;
0034<figref idref="DRAWINGS">FIGS. 12A and 12B</figref> are a top view and a cross-sectional view, respectively, according to one embodiment of the present invention;
0035<figref idref="DRAWINGS">FIGS. 13A to 13D</figref> are each a cross-sectional view according to one embodiment of the present invention;
0036<figref idref="DRAWINGS">FIGS. 14A to 14D</figref> are each a view according to one embodiment of the present invention; and
0037<figref idref="DRAWINGS">FIGS. 15A and 15B</figref> are circuit diagrams for explaining inversion driving.
DETAILED DESCRIPTION OF THE INVENTION
0038Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the present invention can be carried out in many different modes, and it is easily understood by those skilled in the art that modes and details of the present invention can be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the present invention is not interpreted as being limited to the description of the embodiments below. Note that identical portions or portions having the same function in all drawings illustrating the structure of the invention that are described below are denoted by the same reference numerals.
0039Note that the size, the thickness of a layer, a signal waveform, and a region of each structure illustrated in the drawings and the like in the embodiments are exaggerated for simplicity in some cases. Therefore, the embodiments of the present invention are not limited to such scales.
0040Note that terms such as first, second, third to n-th (n is a natural number) employed in this specification are used in order to avoid confusion between components and do not set a limitation on number.
Embodiment 1
0041In this embodiment, a circuit configuration of a pixel included in a display device will be described. Note that, a circuit diagram illustrated in this embodiment illustrates an example in which plural wirings for supplying different signals to plural pixels at the same timing are N (N is a natural number of 3 or larger) data lines (also referred to as signal lines), and different video signals are supplied to the plural pixels in response to scan signals of scan lines.
0042<figref idref="DRAWINGS">FIG. 1A</figref> illustrates a circuit configuration of a pixel included in a display device. <figref idref="DRAWINGS">FIG. 1A</figref> illustrates a circuit configuration in the case where, specifically, three data lines as N (N is a natural number of 3 or larger) data lines (also referred to as signal lines) supply different video signals to three different pixels. A pixel <b>101</b>A includes a transistor (also referred to as a selection transistor) <b>104</b>A and a display element portion <b>105</b>A. In the transistor <b>104</b>A of the pixel <b>101</b>A, a gate terminal is connected to a scan line <b>103</b>A, one terminal (also referred to as a first terminal) to be a source terminal or a drain terminal is connected to a first data line <b>102</b>A, and the other terminal is connected to the display element portion <b>105</b>A. A pixel <b>101</b>B includes a transistor (also referred to as a selection transistor) <b>104</b>B and a display element portion <b>105</b>B. In the transistor <b>104</b>B of the pixel <b>101</b>B, a gate terminal is connected to a scan line <b>103</b>B, one terminal (also referred to as a first terminal) to be a source terminal or a drain terminal is connected to a second data line <b>102</b>B, and the other terminal is connected to the display element portion <b>105</b>B. A pixel <b>101</b>C includes a transistor (also referred to as a selection transistor) <b>104</b>C and a display element portion <b>105</b>C. In the transistor <b>104</b>C of the pixel <b>101</b>C, a gate terminal is connected to a scan line <b>103</b>C, one terminal (also referred to as a first terminal) to be a source terminal or a drain terminal is connected to a third data line <b>102</b>C, and the other terminal is connected to the display element portion <b>105</b>C. The above-described circuit configuration of <figref idref="DRAWINGS">FIG. 1A</figref> is effective in the case where, for example, the transistors <b>104</b>A to <b>104</b>C are brought into conduction (i.e., the transistors <b>104</b>A to <b>104</b>C are turned on) by scan signals through the scan lines <b>103</b>A to <b>103</b>C so that different video signals are supplied to the display element portions <b>105</b>A to <b>105</b>C through the first to third data lines <b>102</b>A to <b>102</b>C.
0043When pixels are arranged in matrix, the first to third data lines <b>102</b>A to <b>102</b>C are provided in the direction substantially orthogonal to the scan lines <b>103</b>A to <b>103</b>C, and the pixel <b>101</b>A including the transistor <b>104</b>A, the pixel <b>101</b>B including the transistor <b>104</b>B, and the pixel <b>101</b>C including the transistor <b>104</b>C are provided along the first data line <b>102</b>A, the second data line <b>102</b>B, and the third data line <b>102</b>C, respectively. The circuit configuration illustrated in <figref idref="DRAWINGS">FIG. 1A</figref> differs from the circuit configuration illustrated in <figref idref="DRAWINGS">FIG. 15A</figref> in that intersection portions between the first to third data lines <b>102</b>A to <b>102</b>C are provided, whereby the first to third data lines <b>102</b>A to <b>102</b>C are provided closest to one terminals of the transistors included in the respective pixels <b>101</b>A to <b>101</b>C. The one terminal of the transistor is connected to the data line provided closest to the terminal.
0044Note that a pixel corresponds to a display unit where luminance of a color element (e.g., any one of R (red), G (green), and B (blue)) can be controlled. Therefore, in the case of a color display device, a minimum display unit of a color image is composed of three pixels of an R pixel, a G pixel, and a B pixel. Note that the color elements for displaying color images are not limited to having three colors, and color elements of more than three colors may be used or a color other than RGB may be used.
0045Note that a transistor is an element having at least three terminals of a gate, a drain, and a source. The transistor includes a channel region between a drain region and a source region, and current can flow through the drain region, the channel region, and the source region. Here, since the source and the drain of the transistor may change depending on the structure, the operating condition, and the like of the transistor, it is difficult to specify which is the source (or the drain). Thus, in this specification, a region functioning as a source or a drain is not called the source or the drain in some cases. In such a case, one of the source and the drain is referred to as one terminal and the other thereof is referred to as the other terminal in some cases. Alternatively, one of the source and the drain may be referred to as a first electrode (terminal) and the other thereof may be referred to as a second electrode (terminal). Further alternatively, one of the source and the drain may be referred to as a source region and the other thereof may be referred to as a drain region. Still further alternatively, one of the source and the drain may be referred to as a source terminal and the other thereof may be referred to as a drain terminal.
0046Note that, in this specification, the description “A is connected to B” includes a case where A is electrically connected to B in addition to a case where A is directly connected to B. Here, the description “A is electrically connected to B” means, when an object having an electric function is placed between A and B, the case where a portion between A and B, which includes the object, can be considered as a node. Specifically, the description “A is connected to B” means the case where a portion between A and B can be regarded as one node in consideration of circuit operation; for example, the case where A and B are connected through a switching element such as a transistor and have the same or substantially the same potentials by conduction of the switching element, or the case where A and B are connected through a resistor and the potential difference generated at two ends of the resistor does not adversely affect the operation of a circuit including A and B.
0047Note that voltage refers to a potential difference between a given potential and a reference potential (e.g., a ground potential) in many cases. Accordingly, voltage, potential, and a potential difference can be referred to as potential, voltage, and a voltage difference, respectively.
0048The structure of a transistor provided in a pixel may be an inverted staggered structure or a staggered structure. Alternatively, a double-gate structure may be used in which a channel region is divided into a plurality of regions and the divided channel regions are connected in series. Alternatively, a dual-gate structure may be used in which gate electrodes are provided over and under the channel region. Further alternatively, a transistor element in which a semiconductor layer forming the transistor is a plurality of island-shaped semiconductor layers to realize switching operation may be used.
0049In <figref idref="DRAWINGS">FIG. 1A</figref>, an intersection portion <b>106</b> is a region where the second data line <b>102</b>B intersects with the third data line <b>102</b>C. An intersection portion <b>107</b> is a region where the first data line <b>102</b>A intersects with the second data line <b>102</b>B. An intersection portion <b>108</b> is a region where the first data line <b>102</b>A intersects with the third data line <b>102</b>C. An intersection portion <b>109</b> is a region where the second data line <b>102</b>B intersects with the third data line <b>102</b>C. An intersection portion <b>110</b> is a region where the first data line <b>102</b>A intersects with the second data line <b>102</b>B. An intersection portion <b>111</b> is a region where the first data line <b>102</b>A intersects with the third data line <b>102</b>C. The first data line <b>102</b>A is provided closest to and is connected to one terminal of the transistor <b>104</b>A without intersection between the one terminal of the transistor <b>104</b>A and another wiring. The second data line <b>102</b>B is provided closest to and is connected to one terminal of the transistor <b>104</b>B without intersection between the one terminal of the transistor <b>104</b>B and another wiring. The third data line <b>102</b>C is provided closest to and is connected to one terminal of the transistor <b>104</b>C without intersection between the one terminal of the transistor <b>104</b>C and another wiring.
0050In the intersection portions <b>106</b> to <b>111</b> illustrated in <figref idref="DRAWINGS">FIG. 1A</figref>, in order to avoid electric short circuit between the first to third data lines <b>102</b>A to <b>102</b>C, one of two data lines intersecting with each other is formed of a different conductive layer. In the intersection portions <b>106</b> to <b>111</b> formed using conductive layers, load capacitance is generated with data lines intersecting with each other. The load capacitance is generated in a region where data lines intersect with each other, that is, a region where a conductive layer which forms the first to third data lines <b>102</b>A to <b>102</b>C intersects with the different conductive layer in the intersection portion.
0051<figref idref="DRAWINGS">FIG. 1B</figref> is a circuit diagram illustrating load capacitance which corresponds to the intersection portions <b>106</b> to <b>111</b> of the first to third data lines <b>102</b>A to <b>102</b>C illustrated in <figref idref="DRAWINGS">FIG. 1A</figref>. In <figref idref="DRAWINGS">FIG. 1B</figref>, as in <figref idref="DRAWINGS">FIG. 1A</figref>, the first data line <b>102</b>A is connected to the first pixel <b>101</b>A, the second data line <b>102</b>B is connected to the second pixel <b>101</b>B, and the third data line <b>102</b>C is connected to the third pixel <b>101</b>C. In <figref idref="DRAWINGS">FIG. 1B</figref>, a capacitor <b>191</b> represents load capacitance due to the intersection portion <b>106</b> in <figref idref="DRAWINGS">FIG. 1A</figref>, a capacitor <b>192</b> represents load capacitance due to the intersection portion <b>107</b> in <figref idref="DRAWINGS">FIG. 1A</figref>, a capacitor <b>193</b> represents load capacitance due to the intersection portion <b>108</b> in <figref idref="DRAWINGS">FIG. 1A</figref>, a capacitor <b>194</b> represents load capacitance due to the intersection portion <b>109</b> in <figref idref="DRAWINGS">FIG. 1A</figref>, a capacitor <b>195</b> represents load capacitance due to the intersection portion <b>110</b> in <figref idref="DRAWINGS">FIG. 1A</figref>, and a capacitor <b>196</b> represents load capacitance due to the intersection portion <b>111</b> in <figref idref="DRAWINGS">FIG. 1A</figref>.
0052As illustrated in <figref idref="DRAWINGS">FIG. 1B</figref>, load capacitance of the capacitor <b>192</b> and the capacitor <b>195</b> is generated with the first data line <b>102</b>A and the second data line <b>102</b>B; load capacitance of the capacitor <b>191</b> and the capacitor <b>194</b> is generated with the second data line <b>102</b>B and the third data line <b>102</b>C; load capacitance of the capacitor <b>193</b> and the capacitor <b>196</b> is generated with the first data line <b>102</b>A and the third data line <b>102</b>C. As described above, load capacitance is generated in a region where the conductive layer which forms the first to third data lines <b>102</b>A to <b>102</b>C intersects with the different conductive layer in the intersection portion. Therefore, in the structure of this embodiment, the widths of the first to third data lines <b>102</b>A to <b>102</b>C are made the same; thus, load capacitance can be uniform between the data lines.
0053Accordingly, in the structure of this embodiment, the areas of the intersection portions formed by the first to third data lines <b>102</b>A to <b>102</b>C can be the same, so that load capacitance can be uniform between the data lines. As a result, the first to third data lines <b>102</b>A to <b>102</b>C each have uniform load capacitance, whereby a signal with a desired potential can be supplied to each pixel. Accordingly, in a display device, deviation in the grayscale and/or signal delay due to a difference in load capacitance between wirings can be reduced.
0054Next, examples of specific display elements in the display element portions <b>105</b>A to <b>105</b>C illustrated in <figref idref="DRAWINGS">FIG. 1A</figref> will be described with reference to <figref idref="DRAWINGS">FIGS. 2A and 2B</figref>. Note that, in the description of <figref idref="DRAWINGS">FIGS. 2A and 2B</figref>, the structures of the elements illustrated in <figref idref="DRAWINGS">FIG. 1A</figref> other than the display element portions <b>105</b>A to <b>105</b>C are not repeatedly described.
0055A circuit diagram of <figref idref="DRAWINGS">FIG. 2A</figref> illustrates an example of the case where the display element portions <b>105</b>A to <b>105</b>C illustrated in <figref idref="DRAWINGS">FIG. 1A</figref> each include a liquid crystal element. The display element portion <b>105</b>A illustrated in <figref idref="DRAWINGS">FIG. 2A</figref> includes a liquid crystal element <b>121</b>A and a capacitor <b>122</b>A which are connected to the other terminal (also referred to as a second terminal) which is to be a source or drain terminal of the transistor <b>104</b>A. The display element portion <b>105</b>B illustrated in <figref idref="DRAWINGS">FIG. 2A</figref> includes a liquid crystal element <b>121</b>B and a capacitor <b>122</b>B which are connected to the other terminal (also referred to as a second terminal) which is to be a source or drain terminal of the transistor <b>104</b>B. The display element portion <b>105</b>C illustrated in <figref idref="DRAWINGS">FIG. 2A</figref> includes a liquid crystal element <b>121</b>C and a capacitor <b>122</b>C which are connected to the other terminal (also referred to as a second terminal) which is to be a source or drain terminal of the transistor <b>104</b>C. One electrode (also referred to as a pixel electrode or a first electrode) of each of the liquid crystal elements <b>121</b>A to <b>121</b>C is connected to the other terminal of each of the transistors <b>104</b>A to <b>104</b>C, respectively. The other electrode (also referred to as a counter electrode or a second electrode) of each of the liquid crystal elements <b>121</b>A to <b>121</b>C is connected to a common potential line (also referred to as a common line). One electrode (also referred to as a first electrode) of each of the capacitors <b>122</b>A to <b>122</b>C is connected to the other terminal of each of the transistors <b>104</b>A to <b>104</b>C, respectively. The other electrode (also referred to as a second electrode) of each of the capacitors <b>122</b>A to <b>122</b>C is connected to a capacitor line. Note that the capacitors <b>122</b>A to <b>122</b>C may be provided as necessary, and can be omitted.
0056A circuit diagram of <figref idref="DRAWINGS">FIG. 2B</figref> illustrates an example of the case where the display element portions <b>105</b>A to <b>105</b>C illustrated in <figref idref="DRAWINGS">FIG. 1A</figref> each include a light-emitting element such as an electro luminescent (EL) element. The display element portion <b>105</b>A illustrated in <figref idref="DRAWINGS">FIG. 2B</figref> includes a light-emitting element <b>123</b>A and a transistor (also referred to as a driving transistor) <b>124</b>A for driving the light-emitting element <b>123</b>A. The display element portion <b>105</b>B illustrated in <figref idref="DRAWINGS">FIG. 2B</figref> includes a light-emitting element <b>123</b>B and a transistor (also referred to as a driving transistor) <b>124</b>B for driving the light-emitting element <b>123</b>B. The display element portion <b>105</b>C illustrated in <figref idref="DRAWINGS">FIG. 2B</figref> includes a light-emitting element <b>123</b>C and a transistor (also referred to as a driving transistor) <b>124</b>C for driving the light-emitting element <b>123</b>C. A gate terminal of each of the transistors <b>124</b>A to <b>124</b>C is connected to the other terminal of each of the transistors <b>104</b>A to <b>104</b>C, respectively. One terminal (also referred to as a first terminal) to be a source or drain terminal of each of the transistors <b>124</b>A to <b>124</b>C is connected to a current supply line (also referred to as a power supply line) for supplying current to the light-emitting elements <b>123</b>A to <b>123</b>C. The other terminal (also referred to as a second terminal) to be a source or drain terminal of each of the transistors <b>124</b>A to <b>124</b>C is connected to one electrode (also referred to as a first electrode) of each of the light-emitting elements <b>123</b>A to <b>123</b>C, respectively. The other electrode (also referred to as a second electrode) of each of the light-emitting elements <b>123</b>A to <b>123</b>C is connected to a ground line (also referred to as a common potential line). In each of the transistors <b>124</b>A to <b>124</b>C, a capacitor may be provided between the gate terminal and the first terminal.
0057Next, a top view of the circuit diagram illustrated in <figref idref="DRAWINGS">FIG. 2A</figref> in which the display element portions <b>105</b>A to <b>105</b>C each include a liquid crystal element is specifically described. The areas of intersection portions formed by the first to third data lines <b>102</b>A to <b>102</b>C are the same and thus load capacitance can be uniform between the data lines. Such advantages will be described below.
0058<figref idref="DRAWINGS">FIG. 3</figref> is a top view of the circuit diagram illustrated in <figref idref="DRAWINGS">FIG. 2A</figref>. Note that, in <figref idref="DRAWINGS">FIG. 3</figref>, description of the capacitors <b>122</b>A to <b>122</b>C illustrated in <figref idref="DRAWINGS">FIG. 2A</figref> is omitted. As the structure corresponding to the liquid crystal elements <b>121</b>A to <b>121</b>C, one electrodes (pixel electrodes) <b>131</b>A to <b>131</b>C of the liquid crystal elements <b>121</b>A to <b>121</b>C are illustrated. The first to third data lines <b>102</b>A to <b>102</b>C illustrated in <figref idref="DRAWINGS">FIG. 3</figref> include a conductive layer (a first conductive layer <b>141</b>) provided in the direction orthogonal to the scan lines <b>103</b>A to <b>103</b>C, and include, in the intersection portions <b>106</b> to <b>111</b>, the conductive layer (a second conductive layer <b>142</b>) which is the same layer as the scan lines <b>103</b>A to <b>103</b>C.
0059In the top view of <figref idref="DRAWINGS">FIG. 3</figref>, in each of the intersection portions <b>106</b> to <b>111</b>, load capacitance is generated in a region where the first conductive layer <b>141</b> overlaps with the second conductive layer <b>142</b>. Specifically, load capacitance is generated in the intersection portion <b>106</b> where the first conductive layer <b>141</b> included in the third data line <b>102</b>C overlaps with the second conductive layer <b>142</b> included in the second data line <b>102</b>B. Load capacitance is generated in the intersection portion <b>107</b> where the first conductive layer <b>141</b> included in the first data line <b>102</b>A overlaps with the second conductive layer <b>142</b> included in the second data line <b>102</b>B. Load capacitance is generated in the intersection portion <b>108</b> where the first conductive layer <b>141</b> included in the first data line <b>102</b>A overlaps with the second conductive layer <b>142</b> included in the third data line <b>102</b>C. Load capacitance is generated in the intersection portion <b>109</b> where the first conductive layer <b>141</b> included in the second data line <b>102</b>B overlaps with the second conductive layer <b>142</b> included in the third data line <b>102</b>C. Load capacitance is generated in the intersection portion <b>110</b> where the first conductive layer <b>141</b> included in the second data line <b>102</b>B overlaps with the second conductive layer <b>142</b> included in the first data line <b>102</b>A. Load capacitance is generated in the intersection portion <b>111</b> where the first conductive layer <b>141</b> included in the third data line <b>102</b>C overlaps with the second conductive layer <b>142</b> included in the first data line <b>102</b>A. The first to third data lines <b>102</b>A to <b>102</b>C have the same number of intersection portions (the intersection portions <b>106</b> to <b>111</b>) formed using the first conductive layer <b>141</b> and the second conductive layer <b>142</b>. Therefore, the widths of the first to third data lines <b>102</b>A to <b>102</b>C are made the same, whereby load capacitance can be uniform between the data lines.
0060Accordingly, in the structure of this embodiment, the areas of the intersection portions formed by the first to third data lines <b>102</b>A to <b>102</b>C can be the same, so that load capacitance can be uniform between the data lines. As a result, the first to third data lines <b>102</b>A to <b>102</b>C each have uniform load capacitance, whereby a signal with a desired potential can be supplied to each pixel. Accordingly, in a display device, deviation in the grayscale and/or signal delay due to a difference in load capacitance between wirings can be reduced.
0061In the case where the conductive layer used for the first conductive layer <b>141</b> and the conductive layer used for the second conductive layer <b>142</b> have different conductivities, wiring resistances of the first to third data lines <b>102</b>A to <b>102</b>C illustrated in <figref idref="DRAWINGS">FIG. 3</figref> might differ from each other. <figref idref="DRAWINGS">FIG. 4A</figref> is a circuit diagram where a resistor corresponds to the second conductive layer <b>142</b> in the top view of <figref idref="DRAWINGS">FIG. 3</figref>.
0062As illustrated in <figref idref="DRAWINGS">FIG. 4A</figref>, the second conductive layer <b>142</b> included in the intersection portion <b>106</b> in <figref idref="DRAWINGS">FIG. 3</figref> is represented by a first resistor <b>151</b>B included in the second data line <b>102</b>B. The second conductive layer <b>142</b> included in the intersection portion <b>107</b> in <figref idref="DRAWINGS">FIG. 3</figref> is represented by a second resistor <b>152</b>B included in the second data line <b>102</b>B. The second conductive layer <b>142</b> included in the intersection portion <b>108</b> in <figref idref="DRAWINGS">FIG. 3</figref> is represented by a first resistor <b>151</b>C included in the third data line <b>102</b>C. The second conductive layer <b>142</b> included in the intersection portion <b>109</b> in <figref idref="DRAWINGS">FIG. 3</figref> is represented by a second resistor <b>152</b>C included in the third data line <b>102</b>C. The second conductive layer <b>142</b> included in the intersection portion <b>110</b> in <figref idref="DRAWINGS">FIG. 3</figref> is represented by a first resistor <b>151</b>A included in the first data line <b>102</b>A. The second conductive layer <b>142</b> included in the intersection portion <b>111</b> in <figref idref="DRAWINGS">FIG. 3</figref> is represented by a second resistor <b>152</b>A included in the first data line <b>102</b>A.
0063As illustrated in <figref idref="DRAWINGS">FIG. 4A</figref>, the structure of this embodiment can be as follows: the first data line <b>102</b>A includes the first resistor <b>151</b>A and the second resistor <b>152</b>A; the second data line <b>102</b>B includes the first resistor <b>151</b>B and the second resistor <b>152</b>B; the third data line <b>102</b>C includes the first resistor <b>151</b>C and the second resistor <b>152</b>C. Thus, in the structure of this embodiment, the number of resistors included in each of the first to third data lines <b>102</b>A to <b>102</b>C can be the same. Therefore, when the second conductive layers <b>142</b> included in the first to third data lines <b>102</b>A to <b>102</b>C are formed using the same conductive material and have the same width, the first to third data lines <b>102</b>A to <b>102</b>C can have the same wiring resistance.
0064Note that the first resistors <b>151</b>A to <b>151</b>C and the second resistors <b>152</b>A to <b>152</b>C in the first to third data lines <b>102</b>A to <b>102</b>C may be provided anywhere in the first to third data lines <b>102</b>A to <b>102</b>C. For example, the second conductive layers <b>142</b> to be resistors may be provided so that resistors are provided as in <figref idref="DRAWINGS">FIG. 4B</figref>.
0065Although the structure of the display device including the first to third data lines as plural wirings for supplying different signals to the plural pixels at the same timing is described in this embodiment, another wiring can be used. For example, the current supply line for supplying current to the light-emitting elements <b>123</b>A to <b>123</b>C in the structure including light-emitting elements described in <figref idref="DRAWINGS">FIG. 2B</figref> may be divided into a first current supply line <b>125</b>A, a second current supply line <b>125</b>B, and a third current supply line <b>125</b>C as illustrated in <figref idref="DRAWINGS">FIG. 5</figref>, and intersection portions <b>161</b> to <b>166</b> may be provided. When the intersection portions <b>161</b> to <b>166</b> are provided in the first current supply line <b>125</b>A, the second current supply line <b>125</b>B, and the third current supply line <b>125</b>C, the first to third current supply lines <b>125</b>A to <b>125</b>C are provided closest to one terminals of the transistors <b>124</b>A to <b>124</b>C, respectively; thus, the one terminals of the transistors <b>124</b>A to <b>124</b>C can be connected to the first to third current supply lines <b>125</b>A to <b>125</b>C, respectively, without intersection between the one terminals of the transistors <b>124</b>A to <b>124</b>C and another wiring.
0066In the structure of this embodiment, in a manner similar to that of the first to third data lines <b>102</b>A to <b>102</b>C, load capacitance can be uniform between the current supply lines. As a result, the first to third current supply lines <b>125</b>A to <b>125</b>C each have uniform load capacitance, whereby a signal with a desired potential can be supplied to each pixel. Accordingly, in a display device, deviation in the grayscale and/or signal delay due to a difference in load capacitance between wirings can be reduced.
0067As described above, a difference in load capacitance can be reduced between data lines or between current supply lines. As the result, deviation in the grayscale and/or signal delay due to the difference in load capacitance can be reduced.
0068This embodiment can be implemented in appropriate combination with any of the structures described in the other embodiments.
Embodiment 2
0069In this embodiment, a structure different from the structure described in Embodiment 1 will be described with reference to <figref idref="DRAWINGS">FIGS. 6A and 6B</figref> and <figref idref="DRAWINGS">FIGS. 7A and 7B</figref>. The structures of this embodiment differs from the structures of <figref idref="DRAWINGS">FIGS. 1A and 1B</figref> and <figref idref="DRAWINGS">FIGS. 2A and 2B</figref> described in Embodiment 1 in that plural scan lines are provided as plural wirings. Specifically, with reference to circuit diagrams, an example where as the plural wirings for supplying different signals to plural pixels at the same timing, N (N is a natural number of 3 or larger) scan lines are provided to supply different scan signals to the plural pixels will be described.
0070<figref idref="DRAWINGS">FIG. 6A</figref> illustrates a circuit configuration of a pixel included in a display device. <figref idref="DRAWINGS">FIG. 6A</figref> illustrates a circuit configuration in the case where three scan lines as N scan lines supply different scan signals to three different pixels. A pixel <b>201</b>A includes a transistor (also referred to as a selection transistor) <b>204</b>A and a display element portion <b>205</b>A. In the transistor <b>204</b>A of the pixel <b>201</b>A, a gate terminal is connected to a first scan line <b>203</b>A, one terminal (also referred to as a first terminal) to be a source or drain terminal is connected to a data line <b>202</b>A, and the other terminal is connected to the display element portion <b>205</b>A. A pixel <b>201</b>B includes a transistor (also referred to as a selection transistor) <b>204</b>B and a display element portion <b>205</b>B. In the transistor <b>204</b>B of the pixel <b>201</b>B, a gate terminal is connected to a second scan line <b>203</b>B, one terminal (also referred to as a first terminal) to be a source or drain terminal is connected to a data line <b>202</b>B, and the other terminal is connected to the display element portion <b>205</b>B. A pixel <b>201</b>C includes a transistor (also referred to as a selection transistor) <b>204</b>C and a display element portion <b>205</b>C. In the transistor <b>204</b>C of the pixel <b>201</b>C, a gate terminal is connected to a third scan line <b>203</b>C, one terminal (also referred to as a first terminal) to be a source or drain terminal is connected to a data line <b>202</b>C, and the other terminal is connected to the display element portion <b>205</b>C. Such a circuit configuration illustrated in <figref idref="DRAWINGS">FIG. 6A</figref> is effective in the case where, for example, the transistors <b>204</b>A to <b>204</b>C are individually brought into conduction (i.e., the transistors <b>204</b>A to <b>204</b>C are turned on) by scan signals through the first to third scan lines <b>203</b>A to <b>203</b>C so that video signals are supplied to the display element portions <b>205</b>A to <b>205</b>C through the data lines <b>202</b>A to <b>202</b>C.
0071When pixels are arranged in matrix, the first to third scan lines <b>203</b>A to <b>203</b>C are provided in the direction orthogonal to the data lines <b>202</b>A to <b>202</b>C, and the pixels <b>201</b>A to <b>201</b>C including the transistors <b>204</b>A to <b>204</b>C, respectively, are provided along the first to third scan lines <b>203</b>A to <b>203</b>C. In the circuit configuration illustrated in <figref idref="DRAWINGS">FIG. 6A</figref>, intersection portions between the first to third scan lines <b>203</b>A to <b>203</b>C are provided; thus, the first to third scan lines <b>203</b>A to <b>203</b>C are provided closest to the respective gate terminals of the transistors included in the pixels <b>201</b>A to <b>201</b>C. Then, the gate terminal of the transistor is connected to the scan line closest to the gate terminal.
0072In <figref idref="DRAWINGS">FIG. 6A</figref>, an intersection portion <b>206</b> is a region where the second scan line <b>203</b>B intersects with the third scan line <b>203</b>C. An intersection portion <b>207</b> is a region where the first scan line <b>203</b>A intersects with the second scan line <b>203</b>B. An intersection portion <b>208</b> is a region where the first scan line <b>203</b>A intersects with the third scan line <b>203</b>C. An intersection portion <b>209</b> is a region where the second scan line <b>203</b>B intersects with the third scan line <b>203</b>C. An intersection portion <b>210</b> is a region where the first scan line <b>203</b>A intersects with the second scan line <b>203</b>B. An intersection portion <b>211</b> is a region where the first scan line <b>203</b>A intersects with the third scan line <b>203</b>C. The first scan line <b>203</b>A is provided closest to a gate terminal of the transistor <b>204</b>A, so that the gate terminal of the transistor <b>204</b>A is connected to the first scan line <b>203</b>A without intersecting with another wiring. The second scan line <b>203</b>B is provided closest to a gate terminal of the transistor <b>204</b>B, so that the gate terminal of the transistor <b>204</b>B is connected to the second scan line <b>203</b>B without intersecting with another wiring. The third scan line <b>203</b>C is provided closest to a gate terminal of the transistor <b>204</b>C, so that the gate terminal of the transistor <b>204</b>C is connected to the third scan line <b>203</b>C without intersecting with another wiring.
0073In the intersection portions <b>206</b> to <b>211</b> illustrated in <figref idref="DRAWINGS">FIG. 6A</figref>, in order to avoid electric short circuit between the first to third scan lines <b>203</b>A to <b>203</b>C, one of two scan lines intersecting with each other is formed of a different conductive layer. In the intersection portions <b>206</b> to <b>211</b> formed using conductive layers, load capacitance is generated with scan lines intersecting with each other. The load capacitance is generated in a region where scan lines intersect with each other, that is, a region where a conductive layer which forms the first to third scan lines <b>203</b>A to <b>203</b>C intersects with the different conductive layer in the intersection portion.
0074<figref idref="DRAWINGS">FIG. 6B</figref> is a circuit diagram illustrating load capacitance which correspond to the intersection portions <b>206</b> to <b>211</b> of the first to third scan lines <b>203</b>A to <b>203</b>C illustrated in <figref idref="DRAWINGS">FIG. 6A</figref>. In <figref idref="DRAWINGS">FIG. 6B</figref>, as in <figref idref="DRAWINGS">FIG. 6A</figref>, the first scan line <b>203</b>A is connected to the first pixel <b>201</b>A, the second scan line <b>203</b>B is connected to the second pixel <b>201</b>B, and the third scan line <b>203</b>C is connected to the third pixel <b>201</b>C. In <figref idref="DRAWINGS">FIG. 6B</figref>, a capacitor <b>291</b> represents a load capacitance due to the intersection portion <b>206</b> in <figref idref="DRAWINGS">FIG. 6A</figref>, a capacitor <b>292</b> represents a load capacitance due to the intersection portion <b>207</b> in <figref idref="DRAWINGS">FIG. 6A</figref>, a capacitor <b>293</b> represents a load capacitance due to the intersection portion <b>208</b> in <figref idref="DRAWINGS">FIG. 6A</figref>, a capacitor <b>294</b> represents a load capacitance due to the intersection portion <b>209</b> in <figref idref="DRAWINGS">FIG. 6A</figref>, a capacitor <b>295</b> represents a load capacitance due to the intersection portion <b>210</b> in <figref idref="DRAWINGS">FIG. 6A</figref>, and a capacitor <b>296</b> represents a load capacitance due to the intersection portion <b>211</b> in <figref idref="DRAWINGS">FIG. 6A</figref>.
0075As illustrated in <figref idref="DRAWINGS">FIG. 6B</figref>, load capacitance of the capacitor <b>292</b> and the capacitor <b>295</b> is generated with the first scan line <b>203</b>A and the second scan line <b>203</b>B; load capacitance of the capacitor <b>291</b> and the capacitor <b>294</b> is generated with the second scan line <b>203</b>B and the third scan line <b>203</b>C; load capacitance of the capacitor <b>293</b> and the capacitor <b>296</b> is generated with the first scan line <b>203</b>A and the third scan line <b>203</b>C. As described above, load capacitance is generated in a region where the conductive layer which forms the first to third scan lines <b>203</b>A to <b>203</b>C intersects with the different conductive layer in the intersection portion. Therefore, in the structure of this embodiment, the widths of the first to third scan lines <b>203</b>A to <b>203</b>C are made the same; thus, load capacitance can be uniform between the scan lines.
0076Accordingly, in the structure of this embodiment, the areas of the intersection portions formed by the first to third scan lines <b>203</b>A to <b>203</b>C can be the same, so that load capacitance can be uniform between the scan lines. As a result, the first to third scan lines <b>203</b>A to <b>203</b>C each have uniform load capacitance, whereby a scan signal can be supplied to each pixel at a desired timing. Accordingly, in a display device, signal delay due to a difference in load capacitance between wirings can be reduced.
0077Next, examples of specific display elements in the display element portions <b>205</b>A to <b>205</b>C illustrated in <figref idref="DRAWINGS">FIG. 6A</figref> will be described with reference to <figref idref="DRAWINGS">FIGS. 7A and 7B</figref>. Note that, in the description of <figref idref="DRAWINGS">FIGS. 7A and 7B</figref>, the structures of the elements illustrated in <figref idref="DRAWINGS">FIG. 6A</figref> other than the display element portions <b>205</b>A to <b>205</b>C are not repeatedly described.
0078A circuit diagram of <figref idref="DRAWINGS">FIG. 7A</figref> illustrates an example of the case where the display element portions <b>205</b>A to <b>205</b>C illustrated in <figref idref="DRAWINGS">FIG. 6A</figref> each include a liquid crystal element. The display element portion <b>205</b>A illustrated in <figref idref="DRAWINGS">FIG. 7A</figref> includes a liquid crystal element <b>221</b>A and a capacitor <b>222</b>A which are connected to the other terminal (also referred to as a second terminal) which is to be a source or drain terminal of the transistor <b>204</b>A. The display element portion <b>205</b>B illustrated in <figref idref="DRAWINGS">FIG. 7A</figref> includes a liquid crystal element <b>221</b>B and a capacitor <b>222</b>B which are connected to the other terminal (also referred to as a second terminal) which is to be a source or drain terminal of the transistor <b>204</b>B. The display element portion <b>205</b>C illustrated in <figref idref="DRAWINGS">FIG. 7A</figref> includes a liquid crystal element <b>221</b>C and a capacitor <b>222</b>C which are connected to the other terminal (also referred to as a second terminal) which is to be a source or drain terminal of the transistor <b>204</b>C. One electrode (also referred to as a pixel electrode or a first electrode) of each of the liquid crystal elements <b>221</b>A to <b>221</b>C is connected to the other terminal of each of the transistors <b>204</b>A to <b>204</b>C, respectively. The other electrode (also referred to as a counter electrode or a second electrode) of each of the liquid crystal elements <b>221</b>A to <b>221</b>C is connected to a common potential line (also referred to as a common line). One electrode (also referred to as a first electrode) of each of the capacitors <b>222</b>A to <b>222</b>C is connected to the other terminal of each of the transistors <b>204</b>A to <b>204</b>C, respectively. The other electrode (also referred to as a second electrode) of each of the capacitors <b>222</b>A to <b>222</b>C is connected to a capacitor line. Note that the capacitors <b>222</b>A to <b>222</b>C may be provided as necessary, and can be omitted.
0079A circuit diagram of <figref idref="DRAWINGS">FIG. 7B</figref> illustrates an example of the case where the display element portions <b>205</b>A to <b>205</b>C illustrated in <figref idref="DRAWINGS">FIG. 6A</figref> each include a light-emitting element such as an electro luminescent (EL) element. The display element portion <b>205</b>A illustrated in <figref idref="DRAWINGS">FIG. 7B</figref> includes a light-emitting element <b>223</b>A and a transistor (also referred to as a driving transistor) <b>224</b>A for driving the light-emitting element <b>223</b>A. The display element portion <b>205</b>B illustrated in <figref idref="DRAWINGS">FIG. 7B</figref> includes a light-emitting element <b>223</b>B and a transistor (also referred to as a driving transistor) <b>224</b>B for driving the light-emitting element <b>223</b>B. The display element portion <b>205</b>C illustrated in <figref idref="DRAWINGS">FIG. 7B</figref> includes a light-emitting element <b>223</b>C and a transistor (also referred to as a driving transistor) <b>224</b>C for driving the light-emitting element <b>223</b>C. A gate terminal of each of the transistors <b>224</b>A to <b>224</b>C is connected to the other terminal of each of the transistors <b>204</b>A to <b>204</b>C, respectively. One terminal (also referred to as a first terminal) to be a source or drain terminal of each of the transistors <b>224</b>A to <b>224</b>C is connected to a current supply line (also referred to as a power supply line) for supplying current to the light-emitting elements <b>223</b>A to <b>223</b>C. The other terminal (also referred to as a second terminal) to be a source or drain terminal of each of the transistors <b>224</b>A to <b>224</b>C is connected to one electrode (also referred to as a first electrode) of each of the light-emitting elements <b>223</b>A to <b>223</b>C, respectively. The other electrode (also referred to as a second electrode) of each of the light-emitting elements <b>223</b>A to <b>223</b>C is connected to a ground line (also referred to as a common potential line). In each of the transistors <b>224</b>A to <b>224</b>C, a capacitor may be provided between the gate terminal and the first terminal.
0080As described above, a difference in load capacitance can be reduced between scan lines. As the result, scan signal delay due to the difference in load capacitance can be reduced.
0081This embodiment can be implemented in appropriate combination with any of the structures described in the other embodiments.
Embodiment 3
0082In this embodiment, an example of a field-sequential display device having the circuit configuration described in Embodiment 1 will be described with reference to <figref idref="DRAWINGS">FIGS. 8A to 8D</figref>, <figref idref="DRAWINGS">FIGS. 9A and 9B</figref>, <figref idref="DRAWINGS">FIGS. 10A and 10B</figref>, and <figref idref="DRAWINGS">FIG. 11</figref>. Note that a display device described in this embodiment is a liquid crystal display device including a liquid crystal element as a display element.
0000<Structural Example of Liquid Crystal Display Device>
0083<figref idref="DRAWINGS">FIG. 8A</figref> illustrates a structural example of a liquid crystal display device. The liquid crystal display device illustrated in <figref idref="DRAWINGS">FIG. 8A</figref> includes a pixel portion <b>30</b>; a scan line driver circuit <b>31</b>; a data line driver circuit (also referred to as a signal line driver circuit) <b>32</b>; <b>3</b><i>n </i>(n is a natural number of 2 or larger) scan lines <b>33</b> which are arranged parallel or substantially parallel to each other and whose potentials are controlled by the scan line driver circuit <b>31</b>; and m (m is a natural number of 2 or larger) first data lines <b>341</b>, m second data lines <b>342</b>, and m third data lines <b>343</b> which are arranged parallel or substantially parallel to each other and whose potentials are controlled by the data line driver circuit <b>32</b>.
0084The pixel portion <b>30</b> is divided into three regions (regions <b>301</b> to <b>303</b>) and each region includes a plurality of pixels which is arranged in matrix (n rows by m columns). Note that each of the scan lines <b>33</b> is connected to m pixels provided in a corresponding row among the plurality of pixels arranged in matrix (<b>3</b><i>n </i>rows by m columns) in the pixel portion <b>30</b>. In addition, each of the first data lines <b>341</b> is connected to n pixels provided in a corresponding column among the plurality of pixels <b>351</b> arranged in matrix (n rows by m columns) in the region <b>301</b>. Further, each of the second data lines <b>342</b> is connected to n pixels provided in a corresponding column among the plurality of pixels <b>352</b> arranged in matrix (n rows by m columns) in the region <b>302</b>. Furthermore, each of the third data lines <b>343</b> is connected to n pixels provided in a corresponding column among the plurality of pixels <b>353</b> arranged in matrix (n rows by m columns) in the region <b>303</b>. Note that intersection portions <b>361</b> are provided as described in Embodiment 1, and the first to third data lines <b>341</b> to <b>343</b> are provided closest to respective one terminals of transistors of pixels in the regions <b>301</b> to <b>303</b>. Thus, load capacitance can be uniform between the first to third data lines <b>341</b> to <b>343</b>. As a result, a video signal with a desired potential can be supplied to each pixel; therefore, deviation in the grayscale and/or signal delay due to a difference in load capacitance between data lines can be reduced.
0085Note that a start signal (GSP) for the scan line driver circuit, the clock signal (GCK) for the scan line driver circuit, and drive power supply potentials such as a high power supply potential and a low power supply potential are input to the scan line driver circuit <b>31</b> from the outside. Further, signals such as the start signal (SSP) for the data line driver circuit, the clock signal (SCK) for the data line driver circuit, and image signals (data<b>1</b> to data<b>3</b>), and drive power supply potentials such as a high power supply potential and a low power supply potential are input to the data line driver circuit <b>32</b> from the outside.
0086<figref idref="DRAWINGS">FIGS. 8B to 8D</figref> illustrate examples of circuit structures of pixels. Specifically, <figref idref="DRAWINGS">FIG. 8B</figref> illustrates an example of the circuit structure of a pixel <b>351</b> provided in the region <b>301</b>; <figref idref="DRAWINGS">FIG. 8C</figref> illustrates an example of the circuit structure of a pixel <b>352</b> provided in the region <b>302</b>; and <figref idref="DRAWINGS">FIG. 8D</figref> illustrates an example of the circuit structure of a pixel <b>353</b> provided in the region <b>303</b>. The pixel <b>351</b> illustrated in <figref idref="DRAWINGS">FIG. 8B</figref> includes a transistor <b>3511</b>, a capacitor <b>3512</b>, and a liquid crystal element <b>3514</b>. A gate terminal of the transistor <b>3511</b> is connected to the scan line <b>33</b>. One terminal of a source and a drain of the transistor <b>3511</b> is connected to the first data line <b>341</b>. One electrode of the capacitor <b>3512</b> is connected to the other terminal of the source and drain of the transistor <b>3511</b>. The other electrode of the capacitor <b>3512</b> is connected to a capacitor line. One electrode (a pixel electrode) of the liquid crystal element <b>3514</b> is connected to the other terminal of the source and the drain of the transistor <b>3511</b> and one electrode of the capacitor <b>3512</b>. The other electrode (a counter electrode) of the liquid crystal element <b>3514</b> is connected to a wiring for supplying a counter potential.
0087The circuit structures of the pixel <b>352</b> illustrated in <figref idref="DRAWINGS">FIG. 8C</figref> and the pixel <b>353</b> illustrated in <figref idref="DRAWINGS">FIG. 8D</figref> are the same as the structure of the pixel <b>351</b> illustrated in <figref idref="DRAWINGS">FIG. 8B</figref>. Note that the pixel <b>352</b> illustrated in <figref idref="DRAWINGS">FIG. 8C</figref> differs from the pixel <b>351</b> illustrated in <figref idref="DRAWINGS">FIG. 8B</figref> in that one of a source and a drain of a transistor <b>3521</b> is connected to the second data line <b>342</b> instead of the first data line <b>341</b>; and the pixel <b>353</b> illustrated in <figref idref="DRAWINGS">FIG. 8D</figref> differs from the pixel <b>351</b> illustrated in <figref idref="DRAWINGS">FIG. 8B</figref> in that one of a source and a drain of a transistor <b>3531</b> is connected to the third data line <b>343</b> instead of the first data line <b>341</b>.
0000<Structural Example of Scan Line Driver Circuit <b>31</b>>
0088<figref idref="DRAWINGS">FIG. 9A</figref> illustrates a structural example of the scan line driver circuit <b>31</b> included in the liquid crystal display device illustrated in <figref idref="DRAWINGS">FIG. 8A</figref>. The scan line driver circuit <b>31</b> illustrated in <figref idref="DRAWINGS">FIG. 9A</figref> includes shift registers <b>311</b> to <b>313</b> each including n output terminals. Note that output terminals of the shift register <b>311</b> are connected to the respective n scan lines <b>33</b> provided in the region <b>301</b>. Output terminals of the shift register <b>312</b> are connected to the respective n scan lines <b>33</b> provided in the region <b>302</b>. Output terminals of the shift register <b>313</b> are connected to the respective n scan lines <b>33</b> provided in the region <b>303</b>. In other words, the shift register <b>311</b> supplies scan signals to the region <b>301</b>; the shift register <b>312</b> supplies scan signals to the region <b>302</b>; and the shift register <b>313</b> supplies scan signals to the region <b>303</b>. Specifically, the shift register <b>311</b> has a function of sequentially shifting scan signals (sequentially selecting the scan lines <b>33</b> every half the period of the clock signal (GCK) for the scan line driver circuit) from the scan line <b>33</b> in a first row in response to the start pulse signal (GSP) for the scan line driver circuit that is input from the outside; the shift register <b>312</b> has a function of sequentially shifting scan signals from the scan line <b>33</b> in the (n+1)th row is respect to the start pulse signal (GSP) for the scan line driver circuit that is input from the outside; and the shift register <b>313</b> has a function of sequentially shifting scan signals from the scan line <b>33</b> in the (2n+1)th row in response to the start pulse signal (GSP) for the scan line driver circuit that is input from the outside.
0000<Operation Example of Scan Line Driver Circuit <b>31</b>>
0089An operation example of the scan line driver circuit <b>31</b> will be described with reference to <figref idref="DRAWINGS">FIG. 9B</figref>. Note that <figref idref="DRAWINGS">FIG. 9B</figref> illustrates the clock signal (GCK) for the scan line driver circuit, signals (SR<b>311</b>out) output from the n output terminals of the shift register <b>311</b>, signals (SR<b>312</b>out) output from the n output terminals of the shift register <b>312</b>, and signals (SR<b>313</b>out) output from the n output terminals of the shift register <b>313</b>.
0090In a sampling period (T<b>1</b>), high-level potentials are sequentially shifted from the scan line <b>33</b> provided in the first row to the scan line <b>33</b> provided in the n-th row every half the cycle of the clock signal (horizontal scan period) in the shift register <b>311</b>; high-level potentials are sequentially shifted from the scan line <b>33</b> provided in the (n+1)th row to the scan line <b>33</b> provided in the 2n-th row every half the cycle of the clock signal (horizontal scan period) in the shift register <b>312</b>; and high-level potentials are sequentially shifted from the scan line <b>33</b> provided in the (2n+1)th row to the scan line <b>33</b> provided in the 3n-th row every half the cycle of the clock signal (horizontal scan period) in the shift register <b>313</b>. Therefore, in the scan line driver circuit <b>31</b>, m pixels <b>351</b> provided in the first row to m pixels <b>351</b> provided in the n-th row are sequentially selected through the scan lines <b>33</b>; m pixels <b>352</b> provided in the (n+1)th row to m pixels <b>352</b> provided in the 2n-th row are sequentially selected; and m pixels <b>353</b> provided in the (2n+1)th row to m pixels <b>353</b> provided in the 3n-th row are sequentially selected. In other words, in the scan line driver circuit <b>31</b>, scan signals can be supplied to 3 m pixels provided in different three rows every horizontal scan period.
0091In a sampling period (T<b>2</b>) and a sampling period (T<b>3</b>), the operation of the shift registers <b>311</b> to <b>313</b> is the same as that in the sampling period (T<b>1</b>). In other words, in the scan line driver circuit <b>31</b>, as in the sampling period (T<b>1</b>), scan signals can be supplied to 3 m pixels provided in given three rows every horizontal scan period.
0000<Structural Example of Data Line Driver Circuit <b>32</b>>
0092<figref idref="DRAWINGS">FIG. 10A</figref> illustrates a structural example of the data line driver circuit <b>32</b> included in the liquid crystal display device illustrated in <figref idref="DRAWINGS">FIG. 8A</figref>. The data line driver circuit <b>32</b> illustrated in <figref idref="DRAWINGS">FIG. 10A</figref> includes a shift register <b>320</b> having m output terminals, m transistors <b>321</b>, m transistors <b>322</b>, and m transistors <b>323</b>. Note that a gate terminal of the transistor <b>321</b> is connected to a j-th output terminal (j is a natural number that is 1 or larger and m or lower) of the shift register <b>320</b>; one terminal of a source and a drain of the transistor <b>321</b> is connected to a wiring for supplying the first image signal (data<b>1</b>); and the other terminal of the source and the drain of the transistor <b>321</b> is connected to the first data line <b>341</b> provided in a j-th column in the pixel portion <b>30</b>. In addition, a gate terminal of the transistor <b>322</b> is connected to the j-th output terminal (j is a natural number that is 1 or larger and m or lower) of the shift register <b>320</b>; one terminal of a source and a drain of the transistor <b>322</b> is connected to a wiring for supplying the second image signal (data<b>2</b>); and the other terminal of the source and the drain of the transistor <b>322</b> is connected to the second data line <b>342</b> provided in the j-th column in the pixel portion <b>30</b>. Further, a gate terminal of the transistor <b>323</b> is connected to the j-th output terminal (j is a natural number that is 1 or larger and m or lower) of the shift register <b>320</b>; one terminal of a source and a drain of the transistor <b>323</b> is connected to a wiring for supplying the third image signal (data<b>3</b>); and the other terminal of the source and the drain of the transistor <b>323</b> is connected to the third data line <b>343</b> provided in the j-th column in the pixel portion <b>30</b>.
0093Note that here, as the first image signal (data<b>1</b>), a red (R) image signal (an image signal held in a pixel when a backlight emits red (R) light), a green (G) image signal, and a blue (B) image signal are supplied to the first data line <b>341</b> in the sampling period (T<b>1</b>), the sampling period (T<b>2</b>), and the sampling period (T<b>3</b>), respectively. In addition, as the second image signal (data<b>2</b>), the blue (B) image signal, the red (R) image signal, and the green (G) image signal are supplied to the second data line <b>342</b> in the sampling period (T<b>1</b>), the sampling period (T<b>2</b>), and the sampling period (T<b>3</b>), respectively. Further, as the third image signal (data<b>3</b>), the green (G) image signal, the blue (B) image signal, and the red (R) image signal are supplied to the third data line <b>343</b> in the sampling period (T<b>1</b>), the sampling period (T<b>2</b>), and the sampling period (T<b>3</b>), respectively.
0000<Structural Example of Backlight>
0094<figref idref="DRAWINGS">FIG. 10B</figref> illustrates a structural example of a backlight provided behind the pixel portion <b>30</b> in the liquid crystal display device illustrated in <figref idref="DRAWINGS">FIG. 8A</figref>. The backlight illustrated in <figref idref="DRAWINGS">FIG. 10B</figref> includes a plurality of backlight units <b>36</b> each including light sources of three colors of red (R), green (G), and blue (B). Note that the plurality of backlight units <b>36</b> is arranged in matrix and lighting of the backlight units <b>36</b> can be controlled every given region. Here, a backlight unit <b>36</b> is provided at least every k rows by m columns (here, k is n/4) as the backlight for the plurality of pixels provided in 3n rows by m columns. Lighting of the backlight units <b>36</b> can be controlled independently. In other words, the backlight can include at least a backlight unit group for the first to k-th rows to a backlight unit group for a (2n+3k+1)th row to the 3n-th row. Lighting of the backlight unit groups can be controlled independently.
0000<Operation Example of Liquid Crystal Display Device>
0095<figref idref="DRAWINGS">FIG. 11</figref> is a view showing scan of a scan signal in the above-mentioned liquid crystal display device and lighting timing for a backlight. In the liquid crystal display device, in the sampling period (T<b>1</b>), the m pixels <b>351</b> in the first row to the m pixels <b>351</b> in the n-th row are sequentially selected; the m pixels <b>352</b> in the (n+1)th row to the m pixels <b>352</b> in the 2n-th row are sequentially selected; and the m pixels <b>353</b> in the (2n+1)th row to the m pixels <b>353</b> in the 3n-th row are sequentially selected. Thus, the image signal can be input to each pixel.
0096As for scan of a scan signal in the liquid crystal display device illustrated in <figref idref="DRAWINGS">FIG. 11</figref> and lighting timing for a backlight, scan of a scan signal and lighting of a backlight unit exhibiting a given color (red (R), green (G), or blue (B)) can be concurrently performed every region (a region in the first row to the n-th row, a region in (n+1)th row to 2n-th row, a region in (2n+1)th row to 3n-th row). In the liquid crystal display device of this embodiment, one image is produced in the pixel portion <b>30</b> by the operations in the sampling periods (T<b>1</b>) to (T<b>3</b>). That is, in the liquid crystal display device, the sampling periods (T<b>1</b>) to (T<b>3</b>) correspond to one frame period.
0000<Liquid Crystal Display Device of this Embodiment>
0097In the liquid crystal display device of this embodiment, load capacitance can be uniform between the first to third data lines <b>341</b> to <b>343</b> for which the structure described in Embodiment 1 can be employed. As a result, a video signal with a desired potential can be supplied to each pixel; therefore, deviation in the grayscale and/or signal delay due to a difference in load capacitance between data lines can be reduced.
0098This embodiment can be implemented in appropriate combination with any of the structures described in the other embodiments.
Embodiment 4
0099In this embodiment, an example of a plan view and a cross-sectional view of a pixel included in a display device, here, a liquid crystal display device will be described with reference to drawings.
0100<figref idref="DRAWINGS">FIG. 12A</figref> is a plane view of one of a plurality of pixels included in a display panel. <figref idref="DRAWINGS">FIG. 12B</figref> is a cross-sectional view taken along the alternate long and short dashed line A-B in <figref idref="DRAWINGS">FIG. 12A</figref>.
0101In <figref idref="DRAWINGS">FIG. 12A</figref>, wiring layers (including source electrode layers <b>1201</b>A to <b>1201</b>C and a drain electrode layer <b>1202</b>) to be the first to third data lines are extended in the vertical direction (in the column direction) in the drawing. Wiring layers (including a gate electrode layer <b>1203</b>) to be scan lines are extended in the direction approximately orthogonal to the source electrode layers <b>1201</b>A to <b>1201</b>C (in the horizontal direction (in the row direction) in the drawing). A capacitor wiring layer <b>1204</b> is extended in the direction approximately parallel to the gate electrode layer <b>1203</b> and in the direction approximately orthogonal to the source electrode layers <b>1201</b>A to <b>1201</b>C (in the horizontal direction (in the row direction) in the drawing). Note that in an intersection portion <b>1209</b>, the source electrode layers <b>1201</b>B and <b>1201</b>C intersect with each other using a wiring layer formed with the same layer as the gate electrode layer <b>1203</b> and the capacitor wiring layer <b>1204</b>.
0102In <figref idref="DRAWINGS">FIG. 12A</figref>, a transistor <b>1205</b> including a gate electrode layer <b>1203</b> is formed in a pixel of the display panel. An insulating film <b>1227</b>, an insulating film <b>1228</b>, and an interlayer film <b>1229</b> are formed over the transistor <b>1205</b>.
0103The pixel of the display panel illustrated in <figref idref="DRAWINGS">FIG. 12A</figref> and <figref idref="DRAWINGS">FIG. 12B</figref> includes a transparent electrode layer <b>1208</b> as a first electrode layer connected to the transistor <b>1205</b>. An opening (a contact hole) is formed in the insulating film <b>1227</b>, the insulating film <b>1228</b>, and the interlayer film <b>1229</b> which are formed over the transistor <b>1205</b>. The transparent electrode layer <b>1208</b> is connected to the transistor <b>1205</b> through the opening (contact hole).
0104The transistor <b>1205</b> illustrated in <figref idref="DRAWINGS">FIGS. 12A and 12B</figref> includes a semiconductor layer <b>1206</b> formed over the gate electrode layer <b>1203</b> with the gate insulating layer <b>1212</b> interposed therebetween; and a source electrode layer <b>1201</b>A and a drain electrode layer <b>1202</b> which are in contact with the semiconductor layer <b>1206</b>. A stack of the capacitor wiring layer <b>1204</b>, the gate insulating layer <b>1212</b>, and the drain electrode layer <b>1202</b> forms a capacitor <b>1207</b>.
0105Further, a first substrate <b>1218</b> included in the transistor <b>1205</b> overlaps with a second substrate <b>1219</b> with a liquid crystal layer <b>1217</b> interposed therebetween.
0106Note that although an example of the case where a bottom-gate inverted staggered transistor is used as the transistor <b>1205</b> is illustrated in <figref idref="DRAWINGS">FIG. 12B</figref>, there is no particular limitation on the structure of a transistor applicable to the liquid crystal display device disclosed in this specification. For example, a top-gate transistor in which a gate electrode layer is placed on the upper side of a semiconductor layer with a gate insulating layer interposed therebetween; or a bottom-gate staggered transistor or planar transistor in which a gate electrode layer is placed on the lower side of a semiconductor layer with a gate insulating layer interposed therebetween can be used.
0107This embodiment can be implemented in appropriate combination with any of the structures described in the other embodiments.
Embodiment 5
0108In this embodiment, an example of a transistor applicable to the liquid crystal display device disclosed in this specification will be described. There is no particular limitation on a structure of the transistor applicable to the liquid crystal display device disclosed in this specification. For example, a staggered transistor, a planar transistor, or the like having a top-gate structure in which a gate electrode is placed on the upper side of a semiconductor layer with a gate insulating layer interposed therebetween or a bottom-gate structure in which a gate electrode is placed on a lower side of a semiconductor layer with a gate insulating layer interposed therebetween, can be used. The transistor may have a single gate structure including one channel formation region, a double gate structure including two channel formation regions, or a triple gate structure including three channel formation regions. Alternatively, the transistor may have a dual gate structure including two gate electrode layers placed over and below a channel region with a gate insulating layer interposed. Examples of the cross-sectional structure of a transistor are illustrated in <figref idref="DRAWINGS">FIGS. 13A to 13D</figref>.
0109Each of the transistors illustrated in <figref idref="DRAWINGS">FIGS. 13A to 13D</figref> uses an oxide semiconductor in its semiconductor layer. An advantage of using an oxide semiconductor is that a high field-effect mobility (the maximum value is 5 cm<sup>2</sup>/Vsec or more, preferably in the range of 10 cm<sup>2</sup>/Vsec to 150 cm<sup>2</sup>/Vsec) can be obtained when a transistor is on, and a low off-state current per unit channel width (e.g., less than 1 aA/μm, preferably less than 10 zA/μm and less than 100 zA/μm at 85° C. per unit channel width) can be obtained when the transistor is off.
0110A transistor <b>410</b> illustrated in <figref idref="DRAWINGS">FIG. 13A</figref> is a bottom-gate transistor and is also referred to as an inverted staggered transistor.
0111The transistor <b>410</b> includes, over a substrate <b>400</b> having an insulating surface, a gate electrode layer <b>401</b>, a gate insulating layer <b>402</b>, an oxide semiconductor layer <b>403</b>, a source electrode layer <b>405</b><i>a</i>, and a drain electrode layer <b>405</b><i>b</i>. An insulating film <b>407</b> is formed to cover the transistor <b>410</b> and to be stacked over the oxide semiconductor layer <b>403</b>. Further, a protective insulating layer <b>409</b> is formed over the insulating film <b>407</b>.
0112A transistor <b>420</b> illustrated in <figref idref="DRAWINGS">FIG. 13B</figref> is a bottom-gate transistor referred to as a channel-protective type (also referred to as a channel-stop type) transistor and is also referred to as an inverted staggered transistor.
0113The transistor <b>420</b> includes, over the substrate <b>400</b> having an insulating surface, the gate electrode layer <b>401</b>, the gate insulating layer <b>402</b>, the oxide semiconductor layer <b>403</b>, an insulating layer <b>427</b> functioning as a channel protective layer covering a channel formation region of the oxide semiconductor layer <b>403</b>, the source electrode layer <b>405</b><i>a</i>, and the drain electrode layer <b>405</b><i>b</i>. Further, the protective insulating layer <b>409</b> is formed to cover the transistor <b>420</b>.
0114A transistor <b>430</b> illustrated in <figref idref="DRAWINGS">FIG. 13C</figref> is a bottom-gate transistor and includes, over the substrate <b>400</b> having an insulating surface, the gate electrode layer <b>401</b>, the gate insulating layer <b>402</b>, the source electrode layer <b>405</b><i>a</i>, the drain electrode layer <b>405</b><i>b</i>, and the oxide semiconductor layer <b>403</b>. The insulating film <b>407</b> is formed to cover the transistor <b>430</b> and to be in contact with the oxide semiconductor layer <b>403</b>. Further, the protective insulating layer <b>409</b> is formed over the insulating film <b>407</b>.
0115In the transistor <b>430</b>, the gate insulating layer <b>402</b> is formed over and in contact with the substrate <b>400</b> and the gate electrode layer <b>401</b>; the source electrode layer <b>405</b><i>a </i>and the drain electrode layer <b>405</b><i>b </i>are formed over and in contact with the gate insulating layer <b>402</b>. The oxide semiconductor layer <b>403</b> is formed over the gate insulating layer <b>402</b>, the source electrode layer <b>405</b><i>a</i>, and the drain electrode layer <b>405</b><i>b. </i>
0116A transistor <b>440</b> illustrated in <figref idref="DRAWINGS">FIG. 13D</figref> is a top-gate transistor. The transistor <b>440</b> includes, over the substrate <b>400</b> having an insulating surface, an insulating layer <b>437</b>, the oxide semiconductor layer <b>403</b>, the source electrode layer <b>405</b><i>a</i>, the drain electrode layer <b>405</b><i>b</i>, the gate insulating layer <b>402</b>, and the gate electrode layer <b>401</b>. A wiring layer <b>436</b><i>a </i>and a wiring layer <b>436</b><i>b </i>are formed in contact with and are connected to the source electrode layer <b>405</b><i>a </i>and the drain electrode layer <b>405</b><i>b</i>, respectively.
0117In this embodiment, the oxide semiconductor layer <b>403</b> is used as a semiconductor layer as described above. Examples of an oxide semiconductor used for the oxide semiconductor layer <b>403</b> include: a four-component metal oxide such as an In—Sn—Ga—Zn—O-based oxide semiconductor; a three-component metal oxide such as an In—Ga—Zn—O-based oxide semiconductor, an In—Sn—Zn—O-based oxide semiconductor, an In—Al—Zn—O-based oxide semiconductor, a Sn—Ga—Zn—O-based oxide semiconductor, an Al—Ga—Zn—O-based oxide semiconductor, and a Sn—Al—Zn—O-based oxide semiconductor; a two-component metal oxide such as an In—Zn—O-based oxide semiconductor, a Sn—Zn—O-based oxide semiconductor, an Al—Zn—O-based oxide semiconductor, a Zn—Mg—O-based oxide semiconductor, a Sn—Mg—O-based oxide semiconductor, and an In—Mg—O-based oxide semiconductor; an In—O-based oxide semiconductor; a Sn—O-based oxide semiconductor; a Zn—O-based oxide semiconductor; and an In—Ga—O-based oxide semiconductor. In addition, SiO<sub>2 </sub>may be contained in the above oxide semiconductor. Here, for example, an In—Ga—Zn—O-based oxide semiconductor means an oxide film containing indium (In), gallium (Ga), and zinc (Zn), and there is no particular limitation on the stoichiometric proportion thereof. The In—Ga—Zn—O-based oxide semiconductor may contain an element other than In, Ga, and Zn.
0118As the oxide semiconductor layer <b>403</b>, a thin film expressed by a chemical formula of InMO<sub>3</sub>(ZnO)<sub>m </sub>(m>0) can be used. Here, M represents one or more metal elements selected from Ga, Al, Mn, and Co. For example, M can be Ga, Ga and Al, Ga and Mn, Ga and Co, or the like.
0119In each of the transistors <b>410</b>, <b>420</b>, <b>430</b>, and <b>440</b> including the oxide semiconductor layer <b>403</b>, the value of current in a transistor in an off state (off-state current value) can be reduced. Therefore, a capacitor for holding an electric signal such as a video signal can be designed to be small in a pixel. This enables improvement in the aperture ratio of a pixel, thereby achieving low power consumption corresponding to the improvement.
0120Further, since the off-state current of the transistors <b>410</b>, <b>420</b>, <b>430</b>, and <b>440</b> including the oxide semiconductor layer <b>403</b> can be reduced, in the pixel, a holding time of an electric signal such as a video signal can be made longer and a writing interval can be set longer. Therefore, the cycle of one frame period can be made longer, and the frequency of a refresh operation performed in a still-image display period can be reduced, thereby further enhancing the effect of suppressing power consumption. In addition, since the transistors can be separately formed in a driver circuit area and a pixel area over one substrate, the number of components of the liquid crystal display device can be reduced.
0121There is no particular limitation on a substrate that can be applied to the substrate <b>400</b> having an insulating surface. For example, a glass substrate made of barium borosilicate glass or aluminosilicate glass can be used.
0122In the bottom-gate transistors <b>410</b>, <b>420</b>, and <b>430</b>, an insulating film serving as a base film may be formed between the substrate and the gate electrode layer. The base film has a function of preventing diffusion of an impurity element from the substrate, and can be a single layer or a stacked layer including one or more of a silicon nitride film, a silicon oxide film, a silicon nitride oxide film, and a silicon oxynitride film.
0123The gate electrode layer <b>401</b> can be a single layer or a stacked layer including any of the following materials: metal materials such as molybdenum, titanium, chromium, tantalum, tungsten, aluminum, copper, neodymium, and scandium; and an alloy material containing any of these materials as its main component.
0124The gate insulating layer <b>402</b> can be a single layer or a stacked layer including any of the following: a silicon oxide layer, a silicon nitride layer, a silicon oxynitride layer, a silicon nitride oxide layer, an aluminum oxide layer, an aluminum nitride layer, an aluminum oxynitride layer, an aluminum nitride oxide layer, and a hafnium oxide layer, and can be formed by a plasma CVD method, a sputtering method, or the like. For example, a 200-nm-thick gate insulating layer is formed in such a manner that a first gate insulating layer that is a silicon nitride layer (SiN<sub>y </sub>(y>0)) having a thickness of 50 nm to 200 nm is formed by a plasma CVD method and then a second gate insulating layer that is a silicon oxide layer (SiO<sub>x </sub>(x>0)) having a thickness of 5 nm to 300 nm is stacked over the first gate insulating layer.
0125As a conductive film used for the source electrode layer <b>405</b><i>a </i>and the drain electrode layer <b>405</b><i>b</i>, for example, a metal film containing an element selected from Al, Cr, Cu, Ta, Ti, Mo, and W and a metal nitride film containing any of the above elements as its component (e.g., a titanium nitride film, a molybdenum nitride film, or a tungsten nitride film) can be used. A metal film having a high melting point such as Ti, Mo, W, or the like or a metal nitride film of any of these elements (e.g., a titanium nitride film, a molybdenum nitride film, or a tungsten nitride film) may be stacked on one or both of a lower side and an upper side of a metal film of Al, Cu, or the like.
0126The same material as that of the source electrode layer <b>405</b><i>a </i>and the drain electrode layer <b>405</b><i>b </i>can be used for conductive films used as the wiring layers <b>436</b><i>a </i>and the wiring layer <b>436</b><i>b </i>which are connected to the source electrode layer <b>405</b><i>a </i>and the drain electrode layer <b>405</b><i>b</i>, respectively.
0127The conductive film to be the source electrode layer <b>405</b><i>a </i>and the drain electrode layer <b>405</b><i>b </i>(including a wiring layer formed using the same layer as the source electrode layer <b>405</b><i>a </i>and the drain electrode layer <b>405</b><i>b</i>) may be formed using conductive metal oxide. As the conductive metal oxide, indium oxide (In<sub>2</sub>O<sub>3</sub>), tin oxide (SnO<sub>2</sub>), zinc oxide (ZnO), an alloy of indium oxide and tin oxide (In<sub>2</sub>O<sub>3</sub>—SnO<sub>2</sub>, abbreviated to ITO), an alloy of indium oxide and zinc oxide (In<sub>2</sub>O<sub>3</sub>—ZnO), and such a metal oxide material containing silicon oxide can be used.
0128As the insulating films <b>407</b> and <b>427</b> being formed over the oxide semiconductor layer and as the insulating layer <b>437</b> being formed below the oxide semiconductor layer, an inorganic insulating film such as a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, or an aluminum oxynitride film can be typically used.
0129For the protective insulating layer <b>409</b> formed over the oxide semiconductor layer, an inorganic insulating film such as a silicon nitride film, an aluminum nitride film, a silicon nitride oxide film, or an aluminum nitride oxide film can be used.
0130Further, a planarization insulating film may be formed over the protective insulating layer <b>409</b> so that surface roughness due to the transistor is reduced. As the planarization insulating film, an organic material such as polyimide, acrylic, and benzocyclobutene can be used. In addition to the above organic materials, a low-dielectric constant material (a low-k material) or the like can be used. Note that the planarization insulating film may be formed by stacking a plurality of insulating films of any of these materials.
0131As described above, the off-state current of a transistor including a highly-purified oxide semiconductor layer formed according to this embodiment can be made low. A highly-purified oxide semiconductor layer is preferable in that it can be formed without a process such as laser irradiation and formation of a transistor over a large-scale substrate can be realized.
0132This embodiment can be implemented in appropriate combination with any of the structures described in the other embodiments.
Embodiment 6
0133A display device disclosed in this specification can be applied to a variety of electronic devices (including a game machine). Examples of electronic devices are a television set (also referred to as a television or a television receiver), a screen of a computer or the like, a camera such as a digital camera or a digital video camera, a digital photo frame, a cellular phone (also referred to as a mobile phone or a cellular phone device), a portable game machine, a personal information terminal, an audio reproducing device, and a large-sized game machine such as a pachinko machine. Examples of an electronic device including the display device described in any of the above embodiments will be described.
0134<figref idref="DRAWINGS">FIG. 14A</figref> illustrates an example of an electronic book device. The electronic book device illustrated in <figref idref="DRAWINGS">FIG. 14A</figref> includes two housings <b>1700</b> and <b>1701</b>. The housings <b>1700</b> and <b>1701</b> are combined with a hinge <b>1704</b> so that the electronic book device can be opened and closed. With such a structure, the electronic book device can be operated like a paper book.
0135A display portion <b>1702</b> and a display portion <b>1703</b> are incorporated in the housing <b>1700</b> and the housing <b>1701</b>, respectively. The display portion <b>1702</b> and the display portion <b>1703</b> may display one image or different images. In the case where the display portions <b>1702</b> and <b>1703</b> display different images, a display portion on the right side (the display portion <b>1702</b> in <figref idref="DRAWINGS">FIG. 14A</figref>) can display text and a display portion on the left side (the display portion <b>1703</b> in <figref idref="DRAWINGS">FIG. 14A</figref>) can display images, for example.
0136<figref idref="DRAWINGS">FIG. 14A</figref> illustrates an example of the case where the housing <b>1700</b> is provided with an operation portion and the like. For example, the housing <b>1700</b> is provided with a power input terminal <b>1705</b>, operation keys <b>1706</b>, a speaker <b>1707</b>, and the like. It is possible to turn the pages with the operation keys <b>1706</b>. Note that a keyboard, a pointing device, or the like may be provided on the surface of the housing, on which the display portion is provided. Further, an external connection terminal (an earphone terminal, a USB terminal, a terminal that can be connected to various cables such as a USB cable, or the like), a recording medium insertion portion, or the like may be provided on the back surface or the side surface of the housing. Furthermore, the electronic book device illustrated in <figref idref="DRAWINGS">FIG. 14A</figref> may have a function of an electronic dictionary.
0137<figref idref="DRAWINGS">FIG. 14B</figref> illustrates an example of a digital photo frame including a display device. For example, in the digital photo frame illustrated in <figref idref="DRAWINGS">FIG. 14B</figref>, a display portion <b>1712</b> is incorporated in a housing <b>1711</b>. The display portion <b>1712</b> can display various images. For example, the display portion <b>1712</b> can display data of an image taken with a digital camera or the like and thus function as a normal photo frame.
0138Note that the digital photo frame illustrated in <figref idref="DRAWINGS">FIG. 14B</figref> is provided with an operation portion, an external connection terminal (a USB terminal, a terminal that can be connected to various cables such as a USB cable, or the like), a recording medium insertion portion, and the like. Although these components may be provided on the surface on which the display portion is provided, it is preferable to provide them on the side surface or the back surface for the design of the digital photo frame. For example, a memory storing data of an image taken with a digital camera is inserted in the recording medium insertion portion of the digital photo frame, so that the image data can be transferred and then displayed on the display portion <b>1712</b>.
0139<figref idref="DRAWINGS">FIG. 14C</figref> illustrates an example of a television set including a display device. In the television set illustrated in <figref idref="DRAWINGS">FIG. 14C</figref>, a display portion <b>1722</b> is incorporated in a housing <b>1721</b>. The display portion <b>1722</b> can display an image. Further, the housing <b>1721</b> is supported by a stand <b>1723</b> here. The display device described in any of the above embodiments can be applied to the display portion <b>1722</b>.
0140The television set illustrated in <figref idref="DRAWINGS">FIG. 14C</figref> can be operated with an operation switch of the housing <b>1721</b> or a separate remote controller. Channels and volume can be controlled with an operation key of the remote controller so that an image displayed on the display portion <b>1722</b> can be controlled. Further, the remote controller may be provided with a display portion for displaying data output from the remote controller.
0141<figref idref="DRAWINGS">FIG. 14D</figref> illustrates an example of a cellular phone including a display device. The cellular phone illustrated in <figref idref="DRAWINGS">FIG. 14D</figref> is provided with a display portion <b>1732</b> incorporated in a housing <b>1731</b>, an operation button <b>1733</b>, an operation button <b>1737</b>, an external connection port <b>1734</b>, a speaker <b>1735</b>, a microphone <b>1736</b>, and the like.
0142The display portion <b>1732</b> of the cellular phone illustrated in <figref idref="DRAWINGS">FIG. 14D</figref> is a touch panel. When the display portion <b>1732</b> is touched with a finger or the like, contents displayed on the display portion <b>1732</b> can be controlled. Further, operations such as making calls and texting can be performed by touching the display portion <b>1732</b> with a finger or the like.
0143This embodiment can be implemented in appropriate combination with any of the structures described in the other embodiments.
0144This application is based on Japanese Patent Application serial no. 2010-129326 filed with Japan Patent Office on Jun. 4, 2010, the entire contents of which are hereby incorporated by reference.
Contents5
17 sheets
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Numbers
- Publication
- 8599347
- Application
- 13117601
Titles
- English
- Display device and electronic device
Patent term adjustment
- A delay
- +160 daysthe office missed an examination deadline
- Applicant delay
- −2 days
- Net adjustment
- 158 days
Classification
- CPC, 4
- G02F1/136286
- G09G3/3225
- G09G3/3648
- G09G2300/0426
- IPC, 2
- G02F1 1343
- H10D30 67